In this paper, we propose a new rotatable antenna (RA) model to improve the performance of wireless communication systems. Different from conventional fixed-position antenna (FPA), the proposed RA system can independently and flexibly change the three-dimensional (3D) orientation of each antenna by adjusting its declination angles to achieve desired channel realizations. Specifically, we study an RA-enabled uplink communication system, where the receive beamforming and the declination angles of all RAs are jointly optimized to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among all the users. In the special single-user and free-space propagation setup, the optimal declination angles are derived in closed form with the maximum-ratio combining (MRC) beamformer applied at the base station (BS). In the general multi-user and multi-path setup, we propose an alternating optimization (AO) algorithm to alternately optimize the receive beamforming and the declination angles in an iterative manner. Simulation results are provided to demonstrate that the proposed RA-enabled system can significantly outperform other benchmark schemes.

翻译：本文提出了一种新型可旋转天线（RA）模型，旨在提升无线通信系统性能。与传统固定位置天线（FPA）不同，所提出的RA系统能够通过调整天线下倾角，独立且灵活地改变每个天线的三维（3D）朝向，从而实现期望的信道状态。具体而言，我们研究了一个基于RA的上行通信系统，其中接收波束成形与所有RA的下倾角被联合优化，以最大化所有用户中的最小信号与干扰加噪声比（SINR）。在特殊的单用户自由空间传播场景下，当基站（BS）采用最大比合并（MRC）波束成形器时，我们以闭合形式推导出了最优下倾角。在一般的多用户多径场景下，我们提出了一种交替优化（AO）算法，以迭代方式交替优化接收波束成形与下倾角。仿真结果表明，所提出的基于RA的系统性能显著优于其他基准方案。